Backside-Illuminated Imager Textured Region Infrared Absorption
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Solution Overview
Problem
Traditional silicon-based photodetecting imagers have limited absorption and detection properties for infrared light due to silicon's indirect bandgap semiconductor nature, making them inefficient for wavelengths longer than 1100 nm, and require substantial path lengths and absorption depths to detect photons effectively.
Innovation Solution
The development of backside-illuminated photosensitive imager devices with a textured region and passivation region that increase the absorption path length for longer wavelengths, allowing for enhanced absorption of infrared radiation within a thin semiconductor material, and include a textured region with surface features to diffuse and redirect electromagnetic radiation, increasing quantum efficiency.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Quantity of substance
If traditional silicon-based photodetecting imagers are used, then the device structure is simple and manufacturing is easy, but the absorption of infrared radiation with wavelengths greater than 1100 nm is very low
Solution Approach 1:
The device is segmented into distinct functional regions: a textured region for light absorption, a passivation region for electrical isolation, and a reflecting region for enhancing light interaction. This segmentation allows each region to be optimized for its specific function, thereby improving infrared absorption without excessive complexity
Solution Approach 2:
The patent introduces a vertical dimension to light absorption by creating a textured surface structure that increases the effective path length of light through the silicon substrate. This dimensional change enables enhanced absorption of infrared radiation without proportionally increasing the device's planar footprint
2Length of stationary object
If the semiconductor substrate is made thinner to reduce device complexity, then manufacturing becomes easier, but the absorption path length for infrared radiation decreases
Solution Approach 1:
The textured region incorporates curved or non-planar surface features that increase the effective absorption path length. This curvature allows thinner substrates to achieve the same absorption effectiveness as thicker planar substrates, balancing manufacturing ease with absorption performance
Solution Approach 2:
A passivation region is introduced as an intermediary layer between the textured region and the junction. This intermediary serves multiple functions: it provides electrical isolation, manages stress, and allows for optimized substrate thickness without compromising device performance or manufacturability
3Measurement precision
If a textured region is added to increase light absorption, then quantum efficiency improves, but the device complexity and manufacturing difficulty increase
Solution Approach 1:
The textured region's geometric parameters (size, shape, spacing) are optimized to achieve high quantum efficiency for infrared wavelengths. By carefully controlling these parameters within specific ranges, the device achieves superior absorption while using established fabrication techniques to manage manufacturing complexity
4Reliability
If the passivation region thickness is increased to improve electrical isolation, then junction isolation improves, but the device complexity and material usage increase
Solution Approach 1:
The passivation region is designed with a thickness that provides sufficient electrical isolation without being excessive. This partial action approach achieves the necessary reliability for junction isolation while minimizing material usage and device complexity
Applied Scientific Principles
This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.
Function Achieved in This Case
These devices achieve improved response in the near-infrared spectrum and enhanced quantum efficiency, with quantum efficiency exceeding 60% in the visible region and increased responsivity for wavelengths greater than 1000 nm, enabling efficient conversion of electromagnetic radiation to electrical signals.
Implementation Method 1
a textured region with surface features to diffuse and redirect electromagnetic radiation, increasing quantum efficiency
Implementation Method 2
enhanced absorption of infrared radiation within a thin semiconductor material
Implementation Method 3
a passivation region positioned between the textured region and the at least one junction. The passivation region is positioned to isolate the at least one junction from the textured region
Implementation Method 4
CMOS sensors are typically manufactured from silicon and can covert visible incident light into a photocurrent
Data Source
AI summary
Backside illuminated photosensitive devices and associated methods are provided. In one aspect, for example, a backside-illuminated photosensitive imager device can include a semiconductor substrate having multiple doped regions forming a least one junction, a textured region coupled to the semiconductor substrate and positioned to interact with electromagnetic radiation, and a passivation region positioned between the textured region and the at least one junction. The passivation region is positioned to isolate the at least one junction from the textured region, and the semiconductor substrate and the textured region are positioned such that incoming electromagnetic radiation passes through the semiconductor substrate before contacting the textured region.Additionally, the device includes an electrical transfer element coupled to the semiconductor substrate to transfer an electrical signal from the at least one junction.